1. Department of Gynecology and Obstetrics, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China
2. Department of Gynecology, The Affiliated Hospital of Jining Medical College, Jining, Shandong 272000, P.R. China
3. Department of Gynecology, The Fourth Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, P.R. China